The present invention relates to a diffuser for aerating a fluid. The diffuser has particular application in the aeration of domestic and industrial waste water. The invention also provides a method for securing a diffuser to a pipe.
Aeration diffusers act by converting a gaseous flow into a stream of fine bubbles in a fluid. Ceramic materials have been used extensively in diffusers for the purpose of forming bubbles. Typically, the ceramic material is in the form of a disk or dome. Fine pores within the ceramic material allow the formation of the bubbles on an outer surface of the ceramic material when an air flow is passed through it. However, when the air flow is stopped, grit and biomass present in surrounding fluid may enter the pores of the ceramic material resulting in the clogging of the diffuser. Accordingly, ceramic material is unsuitable for applications where frequent interruptions to air flow may occur.
Another type of known diffuser consists of a horizontally orientated PVC tube enclosed within an elastomeric sleeve fastened at either end of the tube by clamps in the form of bands. Air is passed through ports in the PVC tube to an annular space formed between the PVC tube and the elastomeric sleeve. As air pressure within the annular space increases small slits in the sleeve open allowing the air to pass through the sleeve and form bubblers on its exterior surface. When the flow of air is stopped the slits in the membrane close thereby inhibiting back flow of fluid into the diffuser. Such diffusers are inefficient as the underside of the sleeve is inoperative and therefore redundant, and bubbles tend to coalesce on the more vertical sides of the sleeve, reducing efficiency.
Elastomeric membranes in the form of a sheet have also been used on disk and rectangular plate type diffusers and have in the past been secured to the diffusers by cover plates and screws, or like means. However, securing in this manner is cumbersome and time consuming.
Known plate diffusers, generally, are relatively small and usually are less than half a metre in diameter or length. This relatively small size necessitates a large number of diffusers and extensive pipe work to connect the required number of diffuser assemblies in a given installation to an air supply, and results in increased assembly time and elevated installation costs.
Piping having specialised, usually threaded, fittings which engage with corresponding fittings on diffusers is used in diffuser installations. The piping is frequently square or round section steel or stainless steel pipe. piping of this type is relatively expensive and the use of such fittings requires extensive preparation of the piping and so also adds to assembly and installation time.
There is, therefore, a need to reduce installation and associated maintenance costs, and to enhance the ease with which aeration diffusers may be installed and maintained.
In a first aspect of the invention there is provided a diffuser for aerating a fluid, comprising:
an elongate base; and
a perforated elastomeric membrane covering a surface of the base and having at least one sealing strip protruding from a face of the membrane and extending along a peripheral region of the membrane;
wherein the at least one sealing strip is engaged in one or more grooves deformed in the base extending in the elongate direction to thereby secure the membrane to the base and seal an interior compartment formed between the face of the membrane and the surface of the base and which receives a flow of gas that permeates through the membrane into the fluid, in use.
The provision of the at least one sealing strip enables the membrane to be secured to the base by simply pressing the sealing strip(s) into the groove or grooves. Similarly, the membrane can be removed by drawing it away from the base such that the at least one sealing strip is pulled from the groove or grooves. Accordingly, assembly of the aerating diffuser and its maintenance can be carried out rapidly. Moreover, more of the peripheral region of the elastomeric membrane may be sealed to the base without the use of cover plates or like means. The elastomeric membrane may be formed from materials such as EPDM, neoprene or silicon rubber.
The diffuser will usually be a plate type diffuser and the base will generally comprise an extrusion. The extrusion may be formed from a plastics material, non-corrosive metal or other suitable substance. Most preferably, the extrusion is an aluminium extrusion. By utilising an extrusion rather than a moulded base for instance, the diffuser may be inexpensively formed to any required length and so substantially minimise production costs as well as the amount of pipework required for a diffuser installation.
In a second aspect of the invention there is provided a diffuser for aerating a fluid, comprising:
a base in the form of an extrusion; and
a perforated member covering a surface of the base and having an inner and an outer face;
wherein the perforated member is secured to the base such that a sealed interior compartment is formed between the inner face of the perforated member and the surface of the base and which receives a flow of gas that permeates through the perforated member into the fluid, in use.
The member will also usually be an elastomeric membrane in such embodiments and can be secured to the base as described above and/or with the aid of clamps or cover plates as is conventionally known.
Broadly, in a third aspect of the invention there is provided a method of installing a diffuser for aerating a fluid, comprising the steps of:
locating a base of the diffuser in a desired position above a substantially horizontally extending pipe; and
using a strap to secure the base of the diffuser to the pipe and hold the base in the desired position.
Generally, an adaptor will be located between the base of the diffuser and the pipe.
In a fourth aspect of the invention there is provided a method of installing a diffuser for aerating a fluid, comprising the steps of:
locating a base of the diffuser above a substantially horizontally extending pipe such that an opening in the base is aligned with an opening in the crown of the pipe to thereby form a through passageway for the passage of a gas from the pipe into an interior compartment of the diffuser; and
using a strap to secure the base of the diffuser to the pipe and hold the opening formed in the base and the opening formed in the pipe in alignment.
If desired, a seal or gasket may be provided between the base of the diffuser and the crown of the pipe to prevent leakage of the fluid from the surrounding environment into the through passageway.
Typically, an adaptor having a passageway for the passage of the gas and which is aligned with the openings will be located between the base and the pipe.
The diffuser can be secured to the pipe with the strap by:
connecting one end of the strap to the diffuser;
drawing the strap around an opposite side of the pipe;
connecting an opposite end of the strap to the diffuser; and
tensioning the strap to thereby secure the diffuser to the pipe.
The method of the invention enables the diffuser to be rapidly installed or removed from the piping of a diffuser installation. The method also allows the diffuser to be fixed directly to a pipe without the need for threaded fittings or such like fixed to the pipe, thereby minimising installation costs.
In a fifth aspect of the invention there is provided an assembly comprising an aerating diffuser secured to a pipe by a strap as described above.
The invention may also provide a kit for use in securing the aerating diffuser to a pipe as well as a kit comprising components of the diffuser of the invention itself.